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Legarda EG, Elena SF, Mushegian AR. Emergence of two distinct spatial folds in a pair of plant virus proteins encoded by nested genes. J Biol Chem 2024; 300:107218. [PMID: 38522515 PMCID: PMC11044054 DOI: 10.1016/j.jbc.2024.107218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 03/15/2024] [Accepted: 03/19/2024] [Indexed: 03/26/2024] Open
Abstract
Virus genomes may encode overlapping or nested open reading frames that increase their coding capacity. It is not known whether the constraints on spatial structures of the two encoded proteins limit the evolvability of nested genes. We examine the evolution of a pair of proteins, p22 and p19, encoded by nested genes in plant viruses from the genus Tombusvirus. The known structure of p19, a suppressor of RNA silencing, belongs to the RAGNYA fold from the alpha+beta class. The structure of p22, the cell-to-cell movement protein from the 30K family widespread in plant viruses, is predicted with the AlphaFold approach, suggesting a single jelly-roll fold core from the all-beta class, structurally similar to capsid proteins from plant and animal viruses. The nucleotide and codon preferences impose modest constraints on the types of secondary structures encoded in the alternative reading frames, nonetheless allowing for compact, well-ordered folds from different structural classes in two similarly-sized nested proteins. Tombusvirus p22 emerged through radiation of the widespread 30K family, which evolved by duplication of a virus capsid protein early in the evolution of plant viruses, whereas lineage-specific p19 may have emerged by a stepwise increase in the length of the overprinted gene and incremental acquisition of functionally active secondary structure elements by the protein product. This evolution of p19 toward the RAGNYA fold represents one of the first documented examples of protein structure convergence in naturally occurring proteins.
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Affiliation(s)
- Esmeralda G Legarda
- Instituto de Biología Integrativa de Sistemas (I2SysBio), CSIC-Universitat de València, Paterna, València, Spain
| | - Santiago F Elena
- Instituto de Biología Integrativa de Sistemas (I2SysBio), CSIC-Universitat de València, Paterna, València, Spain; The Santa Fe Institute, Santa Fe, New Mexico, USA
| | - Arcady R Mushegian
- Division of Molecular and Cellular Biosciences, National Science Foundation, Arlington, Virginia, USA.
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2
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Leastro MO, Pallás V, Sánchez-Navarro JÁ. The capsid protein of citrus leprosis virus C shows a nuclear distribution and interacts with the nucleolar fibrillarin protein. Virus Res 2024; 340:199297. [PMID: 38070688 PMCID: PMC10758971 DOI: 10.1016/j.virusres.2023.199297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 11/29/2023] [Accepted: 12/06/2023] [Indexed: 01/05/2024]
Abstract
Brevipalpus-transmitted viruses (BTVs) have a significant negative economic impact on the citrus industry in Central and South America. Until now, only a few studies have explored the intracellular distribution and interaction of BTVs-encoded proteins with host factors, particularly for cileviruses, the main BTV responsible for the Citrus Leprosis (CL) disease. This study describes the nuclear localization of citrus leprosis virus C (CiLV-C) capsid protein (p29) and its interaction with the fibrillarin (Fib2) within the nucleolar compartment and cell cytoplasm. Our results, obtained by computer predictions and laser scanning confocal microscopy analyses, including colocalization and bimolecular fluorescence complementation (BiFC) approaches, revealed that a fraction of the p29 is localized in the nucleus and colocalizes with the Fib2 in both the nucleolus and cytosol. The nuclear localization of p29 correlated with a smaller nucleus size. Furthermore, co-immunoprecipitation (Co-IP) assays confirmed the interactions between p29 and Fib2. The implications of these findings for the functionalities of the cilevirus capsid protein are discussed.
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Affiliation(s)
- Mikhail Oliveira Leastro
- Instituto de Biología Molecular y Celular de Plantas, Universitat Politècnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), Valencia 46022, Spain.
| | - Vicente Pallás
- Instituto de Biología Molecular y Celular de Plantas, Universitat Politècnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), Valencia 46022, Spain
| | - Jesús Ángel Sánchez-Navarro
- Instituto de Biología Molecular y Celular de Plantas, Universitat Politècnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), Valencia 46022, Spain.
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Leastro MO, Kitajima EW, Pallás V, Sánchez-Navarro JÁ. Rescue of a Cilevirus from infectious cDNA clones. Virus Res 2024; 339:199264. [PMID: 37944757 PMCID: PMC10682248 DOI: 10.1016/j.virusres.2023.199264] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 11/02/2023] [Accepted: 11/06/2023] [Indexed: 11/12/2023]
Abstract
Reverse genetics systems represent an important tool for studying the molecular and functional processes of viral infection. Citrus leprosis virus C (CiLV-C) (genus Cilevirus, family Kitaviridae) is the main pathogen responsible for the citrus leprosis (CL) disease in Latin America, one of the most economically important diseases of the citrus industry. Molecular studies of this pathosystem are limited due to the lack of infectious clones. Here, we report the construction and validation of a CiLV-C infectious cDNA clone based on an agroinfection system. The two viral RNA segments (RNA1 and RNA2) were assembled into two binary vectors (pJL89 and pLXAS). Agroinfiltrated Nicotiana benthamiana plants showed a response similar to that observed in the natural infection process with the formation of localized lesions restricted to the inoculated leaves. The virus recovered from the plant tissue infected with the infectious clones can be mechanically transmitted between N. benthamiana plants. Detection of CiLV-C subgenomic RNAs (sgRNAs) from agroinfiltrated and mechanically inoculated leaves further confirmed the infectivity of the clones. Finally, partial particle-purification preparations or sections of CiLV-C-infected tissue followed by transmission electron microscopy (TEM) analysis showed the formation of CiLV-C virions rescued by the infectious clone. The CiLV-C reverse genetic system now provides a powerful molecular tool to unravel the peculiarities of the CL pathosystem.
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Affiliation(s)
- Mikhail Oliveira Leastro
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Valencia, Spain.
| | - Elliot Watanabe Kitajima
- Departamento de Fitopatologia e Nematologia, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, Brazil
| | - Vicente Pallás
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Valencia, Spain
| | - Jesús Ángel Sánchez-Navarro
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Valencia, Spain.
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Atabekova AK, Solovieva AD, Chergintsev DA, Solovyev AG, Morozov SY. Role of Plant Virus Movement Proteins in Suppression of Host RNAi Defense. Int J Mol Sci 2023; 24:ijms24109049. [PMID: 37240394 DOI: 10.3390/ijms24109049] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 05/28/2023] Open
Abstract
One of the systems of plant defense against viral infection is RNA silencing, or RNA interference (RNAi), in which small RNAs derived from viral genomic RNAs and/or mRNAs serve as guides to target an Argonaute nuclease (AGO) to virus-specific RNAs. Complementary base pairing between the small interfering RNA incorporated into the AGO-based protein complex and viral RNA results in the target cleavage or translational repression. As a counter-defensive strategy, viruses have evolved to acquire viral silencing suppressors (VSRs) to inhibit the host plant RNAi pathway. Plant virus VSR proteins use multiple mechanisms to inhibit silencing. VSRs are often multifunctional proteins that perform additional functions in the virus infection cycle, particularly, cell-to-cell movement, genome encapsidation, or replication. This paper summarizes the available data on the proteins with dual VSR/movement protein activity used by plant viruses of nine orders to override the protective silencing response and reviews the different molecular mechanisms employed by these proteins to suppress RNAi.
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Affiliation(s)
- Anastasia K Atabekova
- A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119992 Moscow, Russia
| | - Anna D Solovieva
- Department of Virology, Biological Faculty, Moscow State University, 119234 Moscow, Russia
| | - Denis A Chergintsev
- Department of Virology, Biological Faculty, Moscow State University, 119234 Moscow, Russia
| | - Andrey G Solovyev
- A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119992 Moscow, Russia
- Department of Virology, Biological Faculty, Moscow State University, 119234 Moscow, Russia
| | - Sergey Y Morozov
- A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119992 Moscow, Russia
- Department of Virology, Biological Faculty, Moscow State University, 119234 Moscow, Russia
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Orchid fleck dichorhavirus movement protein shows RNA silencing suppressor activity. J Gen Virol 2022; 103. [DOI: 10.1099/jgv.0.001805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
To counteract RNA interference-mediated antiviral defence, virus genomes evolved to express proteins that inhibit this plant defence mechanism. Using six independent biological approaches, we show that orchid fleck dichorhavirus citrus strain (OFV-citrus) movement protein (MP) may act as a viral suppressor of RNA silencing (VSR). By using the alfalfa mosaic virus (AMV) RNA 3 expression vector, it was observed that the MP triggered necrosis response in transgenic tobacco leaves and increased the viral RNA (vRNA) accumulation. The use of the potato virus X (PVX) expression system revealed that the cis expression of MP increased both the severity of the PVX infection and the accumulation of PVX RNAs, further supporting that MP could act as an RNA silencing suppressor (RSS). From the analysis of the RSS-defective turnip crinkle virus (TCV), we do not find local RSS activity for MP, suggesting a link between MP suppressor activity and the prevention of systemic silencing. In the analysis of local suppressive activity using the GFP-based agroinfiltration assay in Nicotiana benthamiana (16 c line), we do not identify local RSS activity for the five OFV RNA1-encoded proteins. However, when evaluating the small interfering RNA (siRNA) accumulation, we find that the expression of MP significantly reduces the accumulation of GFP-derived siRNA. Finally, we examine whether the MP can prevent systemic silencing in 16c plants. Our findings show that MP inhibits the long-distance spread of RNA silencing, but does not affect the short-distance spread. Together, our findings indicate that MP is part of OFV’s counter-defence mechanism, acting mainly in the prevention of systemic long-distance silencing. This work presents the first report of a VSR for a member of the genus Dichorhavirus.
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Leastro MO, Villar-Álvarez D, Freitas-Astúa J, Kitajima EW, Pallás V, Sánchez-Navarro JÁ. Spontaneous Mutation in the Movement Protein of Citrus Leprosis Virus C2, in a Heterologous Virus Infection Context, Increases Cell-to-Cell Transport and Generates Fitness Advantage. Viruses 2021; 13:v13122498. [PMID: 34960766 PMCID: PMC8708801 DOI: 10.3390/v13122498] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 11/30/2021] [Accepted: 12/08/2021] [Indexed: 11/16/2022] Open
Abstract
Previous results using a movement defective alfalfa mosaic virus (AMV) vector revealed that citrus leprosis virus C (CiLV-C) movement protein (MP) generates a more efficient local movement, but not more systemic transport, than citrus leprosis virus C2 (CiLV-C2) MP, MPs belonging to two important viruses for the citrus industry. Here, competition experiment assays in transgenic tobacco plants (P12) between transcripts of AMV constructs expressing the cilevirus MPs, followed by several biological passages, showed the prevalence of the AMV construct carrying the CiLV-C2 MP. The analysis of AMV RNA 3 progeny recovered from P12 plant at the second viral passage revealed the presence of a mix of progeny encompassing the CiLV-C2 MP wild type (MPWT) and two variants carrying serines instead phenylalanines at positions 72 (MPS72F) or 259 (MPS259F), respectively. We evaluated the effects of each modified residue in virus replication, and cell-to-cell and long-distance movements. Results indicated that phenylalanine at position 259 favors viral cell-to-cell transport with an improvement in viral fitness, but has no effect on viral replication, whereas mutation at position 72 (MPS72F) has a penalty in the viral fitness. Our findings indicate that the prevalence of a viral population may be correlated with its greater efficiency in cell-to-cell and systemic movements.
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Affiliation(s)
- Mikhail Oliveira Leastro
- Unidade Laboratorial de Referência em Biologia Molecular Aplicada, Instituto Biológico, São Paulo 04014-900, Brazil;
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), 46022 Valencia, Spain; (D.V.-Á.); (V.P.)
- Correspondence: (M.O.L.); (J.Á.S.-N.)
| | - David Villar-Álvarez
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), 46022 Valencia, Spain; (D.V.-Á.); (V.P.)
| | - Juliana Freitas-Astúa
- Unidade Laboratorial de Referência em Biologia Molecular Aplicada, Instituto Biológico, São Paulo 04014-900, Brazil;
- Embrapa Mandioca e Fruticultura, Cruz das Almas 70770-901, Brazil
| | - Elliot Watanabe Kitajima
- Departamento de Fitopatologia e Nematologia, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba 13418-900, Brazil;
| | - Vicente Pallás
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), 46022 Valencia, Spain; (D.V.-Á.); (V.P.)
| | - Jesús Ángel Sánchez-Navarro
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), 46022 Valencia, Spain; (D.V.-Á.); (V.P.)
- Correspondence: (M.O.L.); (J.Á.S.-N.)
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Membrane Association and Topology of Citrus Leprosis Virus C2 Movement and Capsid Proteins. Microorganisms 2021; 9:microorganisms9020418. [PMID: 33671330 PMCID: PMC7922530 DOI: 10.3390/microorganisms9020418] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/09/2021] [Accepted: 02/11/2021] [Indexed: 01/04/2023] Open
Abstract
Although citrus leprosis disease has been known for more than a hundred years, one of its causal agents, citrus leprosis virus C2 (CiLV-C2), is poorly characterized. This study described the association of CiLV-C2 movement protein (MP) and capsid protein (p29) with biological membranes. Our findings obtained by computer predictions, chemical treatments after membrane fractionation, and biomolecular fluorescence complementation assays revealed that p29 is peripherally associated, while the MP is integrally bound to the cell membranes. Topological analyses revealed that both the p29 and MP expose their N- and C-termini to the cell cytoplasmic compartment. The implications of these results in the intracellular movement of the virus were discussed.
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Leastro MO, Freitas-Astúa J, Kitajima EW, Pallás V, Sánchez-Navarro JA. Unravelling the involvement of cilevirus p32 protein in the viral transport. Sci Rep 2021; 11:2943. [PMID: 33536554 PMCID: PMC7859179 DOI: 10.1038/s41598-021-82453-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 01/13/2021] [Indexed: 12/04/2022] Open
Abstract
Citrus leprosis (CL) is a severe disease that affects citrus orchards mainly in Latin America. It is caused by Brevipalpus-transmitted viruses from genera Cilevirus and Dichorhavirus. Currently, no reports have explored the movement machinery for the cilevirus. Here, we have performed a detailed functional study of the p32 movement protein (MP) of two cileviruses. Citrus leprosis-associated viruses are not able to move systemically in neither their natural nor experimental host plants. However, here we show that cilevirus MPs are able to allow the cell-to-cell and long-distance transport of movement-defective alfalfa mosaic virus (AMV). Several features related with the viral transport were explored, including: (i) the ability of cilevirus MPs to facilitate virus movement on a nucleocapsid assembly independent-manner; (ii) the generation of tubular structures from transient expression in protoplast; (iii) the capability of the N- and C- terminus of MP to interact with the cognate capsid protein (p29) and; (iv) the role of the C-terminus of p32 in the cell-to-cell and long-distance transport, tubule formation and the MP-plasmodesmata co-localization. The MP was able to direct the p29 to the plasmodesmata, whereby the C-terminus of MP is independently responsible to recruit the p29 to the cell periphery. Furthermore, we report that MP possess the capacity to enter the nucleolus and to bind to a major nucleolar protein, the fibrillarin. Based on our findings, we provide a model for the role of the p32 in the intra- and intercellular viral spread.
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Affiliation(s)
- Mikhail Oliveira Leastro
- Unidade Laboratorial de Referência em Biologia Molecular Aplicada, Instituto Biológico, São Paulo, SP, Brazil. .,Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain.
| | - Juliana Freitas-Astúa
- Unidade Laboratorial de Referência em Biologia Molecular Aplicada, Instituto Biológico, São Paulo, SP, Brazil.,Embrapa Mandioca e Fruticultura, Cruz das Almas, BA, Brazil
| | - Elliot Watanabe Kitajima
- Departamento de Fitopatologia e Nematologia, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, SP, Brazil
| | - Vicente Pallás
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain
| | - Jesús A Sánchez-Navarro
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain.
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